Preheat oven to 350F. Brush an ovenproof skillet (cast iron is best) with
1 tbsp melted butter.
Stir flour with baking powder and salt in a large bowl. Stir butter with water in a small bowl, then stir into flour mixture until it comes together. Dough will be a little sticky. Transfer into the prepared skillet. Spread dough to edges and pat down. Sprinkle with cheddar and pat gently so cheese sticks to dough.
Bake in centre of oven until golden and a cake tester inserted into the centre comes out clean, 35 to 40 min. Keep bannock in skillet. Cut into wedges.